Transforming growth factor beta1 regulates melanocyte proliferation and differentiation in mouse neural crest cells via stem cell factor/KIT signaling

Single-Cell RNA Sequencing Unravels Heterogeneity of the Stromal Niche in Cutaneous Melanoma Heterogeneous Spheroids

Heterogeneous spheroids have recently acquired a prominent position in melanoma research because they incorporate microenvironmental cues relevant for melanoma. In this study, we focused on the analysis of microenvironmental factors introduced in melanoma heterogeneous spheroids by different dermal fibroblasts. We aimed to map the fibroblast diversity resulting from previously acquired damage caused by exposure to extrinsic and intrinsic stimuli. To construct heterogeneous melanoma spheroids, we used normal dermal fibroblasts from the sun-protected skin of a juvenile donor. We compared them to the fibroblasts from the sun-exposed photodamaged skin of an adult donor. Further, we analysed the spheroids by single-cell RNA sequencing. To validate transcriptional data, we also compared the immunohistochemical analysis of heterogeneous spheroids to melanoma biopsies. We have distinguished three functional clusters in primary human fibroblasts from melanoma spheroids. These clusters differed in the expression of (a) extracellular matrix-related genes, (b) pro-inflammatory factors, and (c) TGFβ signalling superfamily. We observed a broader deregulation of gene transcription in previously photodamaged cells. We have confirmed that pro-inflammatory cytokine IL-6 significantly enhances melanoma invasion to the extracellular matrix in our model. This supports the opinion that the aspects of ageing are essential for reliable melanoma 3D modelling in vitro.

Chemical induced pathognomonic features observed in human vitiligo are mediated through miR-2909 RNomics pathway

BACKGROUND

Chemicals like Monobenzyl Ether of Hydroquinone (MBEH) and 4-Tertiary Butyl Phenol (4-TBP) have been widely recognized to induce clinical lesions that resemble vitiligo, but exact molecular pathway through which these chemicals initiate vitiligo is still far from clear.

OBJECTIVES

Since vitiligo is widely considered as an autoimmune disease, this study was an attempt to understand miR-2909 RNomics in vitiligo pathogenesis using MBEH treated primary melanocytes as an archetype cellular model because MBEH causes pathological features indistinguishable from clinical vitiligo.

METHODS

Primary melanocytes were treated with MBEH and 4-TBP and the role of miR-2909 RNomics at transcriptional and translational level was explored through qRT-PCR, western blot analysis, flow cytometry, immunocytochemistry, immunohistochemistry and in silico binding affinities. 4 mm punch biopsies were also obtained from lesional sites of vitiligo patients to validate the results observed in cell culture experiments.

RESULTS

MBEH induced miR-2909 RNomics led to downregulation of MITF, TYR, TYRP1, and TYRP2 leading to decreased melanin synthesis which in turn is a characteristic trait of vitiligo. On the other hand, 4-TBP increased TGF-β which also has the intrinsic capacity to downregulate MITF leading to decreased melanin synthesis and thereby initiation of vitiligo.

CONCLUSION

Based upon our results we propose a molecular pathway which has the inherent capacity to resolve the mechanism through which these chemicals may induce vitiligo. This mechanism was also found to be involved in the lesional biopsies of vitiligo patients. These results could be exploited in better understanding the pathogenesis as well as in treatment of vitiligo.

Revealing the complex genetic architecture of obsessive-compulsive disorder using meta-analysis

Two obsessive-compulsive disorder (OCD) genome-wide association studies (GWASs) have been published by independent OCD consortia, the International Obsessive-Compulsive Disorder Foundation Genetics Collaborative (IOCDF-GC) and the OCD Collaborative Genetics Association Study (OCGAS), but many of the top-ranked signals were supported in only one study. We therefore conducted a meta-analysis from the two consortia, investigating a total of 2688 individuals of European ancestry with OCD and 7037 genomically matched controls. No single-nucleotide polymorphisms (SNPs) reached genome-wide significance. However, in comparison with the two individual GWASs, the distribution of P-values shifted toward significance. The top haplotypic blocks were tagged with rs4733767 (P=7.1 × 10^-7; odds ratio (OR)=1.21; confidence interval (CI): 1.12-1.31, CASC8/CASC11), rs1030757 (P=1.1 × 10^-6; OR=1.18; CI: 1.10-1.26, GRID2) and rs12504244 (P=1.6 × 10^-6; OR=1.18; CI: 1.11-1.27, KIT). Variants located in or near the genes ASB13, RSPO4, DLGAP1, PTPRD, GRIK2, FAIM2 and CDH20, identified in linkage peaks and the original GWASs, were among the top signals. Polygenic risk scores for each individual study predicted case-control status in the other by explaining 0.9% (P=0.003) and 0.3% (P=0.0009) of the phenotypic variance in OCGAS and the European IOCDF-GC target samples, respectively. The common SNP heritability in the combined OCGAS and IOCDF-GC sample was estimated to be 0.28 (s.e.=0.04). Strikingly, ∼65% of the SNP-based heritability in the OCGAS sample was accounted for by SNPs with minor allele frequencies of ⩾40%. This joint analysis constituting the largest single OCD genome-wide study to date represents a major integrative step in elucidating the genetic causes of OCD.

Aberrant DNA methylation of GATA binding protein 3 (GATA3), interleukin-4 (IL-4), and transforming growth factor-β (TGF-β) promoters in Behcet's disease

The pathogenesis of Behcet's disease (BD) remains poorly understood. The purpose of this study was to investigate whether an aberrant DNA methylation of transcriptional and inflammatory factors, including TBX21, GATA3, RORγt, FOXP3, IFN-γ, IL-4, IL-17A and TGF-β, in CD4⁺T confers risk to BD. We found that the promoter methylation level of GATA3, IL-4 and TGF-β was significantly up-regulated in active BD patients and negatively correlated with the corresponding mRNA expression. The mRNA expression of GATA3 and TGF-β was markedly down-regulated in active BD patients compared to healthy individuals. Treatment with corticosteroids and cyclosporine (CsA) resulted in a decrease of the methylation level of GATA3 and TGF-β in inactive BD patients. Our results suggest that an aberrant DNA methylation of GATA3 and TGF-β is associated with their mRNA expression and participates in the pathogenesis of BD.

Paracrine Secreted Frizzled-Related Protein 4 Inhibits Melanocytes Differentiation in Hair Follicle

Wnt signaling plays crucial role in regulating melanocyte stem cells/melanocyte differentiation in the hair follicle. However, how the Wnt signaling is balanced to be overactivated to control follicular melanocytes behavior remains unknown. Here, by using immunofluorescence staining, we showed that secreted frizzled-related protein 4 (sFRP4) is preferentially expressed in the skin epidermal cells rather than in melanocytes. By overexpression of sFRP4 in skin cells in vivo and in vitro, we found that sFRP4 attenuates activation of Wnt signaling, resulting in decrease of melanocytes differentiation in the regenerating hair follicle. Our findings unveiled a new regulator that involves modulating melanocytes differentiation through a paracrine mechanism in hair follicle, supplying a hope for potential therapeutic application to treat skin pigmentation disorders.

Germline mutations of KIT in gastrointestinal stromal tumor (GIST) and mastocytosis

Somatic mutations of KIT are frequently found in mastocytosis and gastrointestinal stromal tumor (GIST), while germline mutations of KIT are rare, and only found in few cases of familial GIST and mastocytosis. Although ligand-independent activation is the common feature of KIT mutations, the phenotypes mediated by various germline KIT mutations are different. Germline KIT mutations affect different tissues such as interstitial cells of Cajal (ICC), mast cells or melanocytes, and thereby lead to GIST, mastocytosis, or abnormal pigmentation. In this review, we summarize germline KIT mutations in familial mastocytosis and GIST and discuss the possible cellular context dependent transforming activity of KIT mutations.

Characterization of cultured multipotent zebrafish neural crest cells

The neural crest is a unique cell population associated with vertebrate evolution. Neural crest cells (NCCs) are characterized by their multipotent and migratory potentials. While zebrafish is a powerful genetic model organism, the isolation and culture of zebrafish NCCs would provide a useful adjunct to fully interrogate the genetic networks that regulate NCC development. Here we report for the first time the isolation, in vitro culture, and characterization of NCCs from zebrafish embryos. NCCs were isolated from transgenic sox10:egfp embryos using fluorescence activated cell sorting and cultured in complex culture medium without feeder layers. NCC multilineage differentiation was determined by immunocytochemistry and real-time qPCR, cell migration was assessed by wound healing assay, and the proliferation index was calculated by immunostaining against the mitosis marker phospho-histone H3. Cultured NCCs expressed major neural crest lineage markers such as sox10, sox9a, hnk1, p75, dlx2a, and pax3, and the pluripotency markers c-myc and klf4. We showed that the cultured NCCs can be differentiated into multiple neural crest lineages, contributing to neurons, glial cells, smooth muscle cells, melanocytes, and chondrocytes. We applied the NCC in vitro model to study the effect of retinoic acid on NCC development. We showed that retinoic acid had a profound effect on NCC morphology and differentiation, significantly inhibited proliferation and enhanced cell migration. The availability of high numbers of NCCs and reproducible functional assays offers new opportunities for mechanistic studies of neural crest development, in genetic and chemical biology applications.

Heterotaxin: a TGF-β signaling inhibitor identified in a multi-phenotype profiling screen in Xenopus embryos

Disruptions of anatomical left-right asymmetry result in life-threatening heterotaxic birth defects in vital organs. We performed a small molecule screen for left-right asymmetry phenotypes in Xenopus embryos and discovered a pyridine analog, heterotaxin, which disrupts both cardiovascular and digestive organ laterality and inhibits TGF-β-dependent left-right asymmetric gene expression. Heterotaxin analogs also perturb vascular development, melanogenesis, cell migration, and adhesion, and indirectly inhibit the phosphorylation of an intracellular mediator of TGF-β signaling. This combined phenotypic profile identifies these compounds as a class of TGF-β signaling inhibitors. Notably, heterotaxin analogs also possess highly desirable antitumor properties, inhibiting epithelial-mesenchymal transition, angiogenesis, and tumor cell proliferation in mammalian systems. Our results suggest that assessing multiple organ, tissue, cellular, and molecular parameters in a whole organism context is a valuable strategy for identifying the mechanism of action of bioactive compounds.

Expression of the embryonic morphogen Nodal in cutaneous melanocytic lesions

Nodal, a potent embryonic morphogen in the transforming growth factor-beta family, is a proposed key regulator of melanoma tumorigenicity. However, there has been no systematic study of Nodal expression in melanocytic lesions. We investigated Nodal expression by immunohistochemistry in 269 melanocytic lesions, including compound nevi, dysplastic nevi, congenital nevi, Spitz nevi, melanoma in situ, malignant melanoma including the variant desmoplastic melanoma, and metastatic melanoma. We found that the Nodal expression was significantly increased in malignant lesions (including melanoma in situ, malignant melanoma, and metastatic melanoma) compared with compound nevi, Spitz nevi, and dysplastic nevi. Surprisingly, congenital nevi expressed a level of Nodal comparable with malignant lesions, whereas desmoplastic melanoma showed lower expression than nondesmoplastic malignant melanoma (P<0.05). Deep melanoma (Breslow depth >1 mm) displayed a higher percentage of Nodal-positive tumor cells than did superficial melanoma (Breslow depth < or =1 mm), although there was no statistical difference in the overall staining intensity (P=0.18). Melanomas in situ showed a lower level of Nodal expression than did deep melanomas and metastatic melanomas (P<0.05). The low expression of Nodal in normal and dysplastic nevi, and its increasing expression with the progression of malignant lesions, are suggestive of a role for Nodal in melanoma progression.

Receptor tyrosine kinases in sinonasal undifferentiated carcinomas--evaluation for EGFR, c-KIT, and HER2/neu expression

BACKGROUND

Our objective was to identify the expression of epidermal growth factor receptor (EGFR), c-KIT (CD117), and HER2/neu in sinonasal undifferentiated carcinoma (SNUC).

METHODS

Immunohistochemistry for c-KIT (CD117), EGFR, and HER2/neu was performed on paraffin-embedded tissue from SNUC cases. A search for activating mutations in c-kit exons 9, 11, 13, and 17 or gene amplification was undertaken by high-resolution DNA melting curve analysis and fluorescence in situ hybridization (FISH) for c-kit and chromosome 4, respectively.

RESULTS

By immunohistochemistry, 9 of 11 cases (81.8%) were diffusely (4+) positive for c-KIT, 3 of 11 cases (27.3%) were positive for EGFR, and none of the cases were positive for HER2/neu. Neither activating mutations nor gene amplification of c-kit were detected in any of the 8 assessable tumors.

CONCLUSION

c-KIT is frequently expressed in SNUC. However, the overexpression is not due to activating mutations or gene amplification.

Control of KIT signalling in male germ cells: what can we learn from other systems?

The KIT ligand (KITL)/KIT-signalling system is among several pathways known to be essential for fertility. In the postnatal testis, the KIT/KITL interaction is crucial for spermatogonial proliferation, differentiation, survival and subsequent entry into meiosis. Hence, identification of endogenous factors that regulate KIT synthesis is important for understanding the triggers driving germ cell maturation. Although limited information is available regarding local factors in the testicular microenvironment that modulate KIT synthesis at the onset of spermatogenesis, knowledge from other systems could be used as a basis for identifying how KIT function is regulated in germ cells. This review describes the known regulators of KIT, including transcription factors implicated in KIT promoter regulation. In addition, specific downstream outcomes in biological processes that KIT orchestrates are addressed. These are discussed in relationship to current knowledge of mammalian germ cell development.

Neurogenic niche modulation by activated microglia: transforming growth factor beta increases neurogenesis in the adult dentate gyrus

Adult neural stem cells (NSC) proliferate and differentiate depending on the composition of the cellular and molecular niche in which they are immersed. Until recently, microglial cells have been ignored as part of the neurogenic niche. We studied the dynamics of NSC proliferation and differentiation in the dentate gyrus of the hippocampus (DG) and characterized the changes of the neurogenic niche in adrenalectomized animals (ADX). At the cellular level, we found increased NSC proliferation and neurogenesis in the ADX animals. In addition, a morphologically distinct subpopulation of NSC (Nestin+/GFAP-) with increased proliferating profile was detected. Interestingly, the number of microglial cells at stages 2 and 3 of activation correlated with increased neurogenesis (r2 = 0.999) and the number of Nestin-positive cells (r2 = 0.96). At the molecular level, transforming growth factor beta (TGF-beta) mRNA levels were increased 10-fold in ADX animals. Interestingly, TGF-beta levels correlated with the amount of neurogenesis detected (r2 = 0.99) and the number of stage 2 and 3 microglial cells (r2 = 0.94). Furthermore, blockade of TGF-beta biological activity by administration of an anti-TGF-beta type II receptor antibody diminished the percentage of 5-bromo-2'-deoxyuridine (BrdU)/PSA-NCAM-positive cells in vivo. Moreover, TGF-beta was able to promote neurogenesis in NSC primary cultures. This work supports the idea that activated microglial cells are not pro- or anti-neurogenic per se, but the balance between pro- and anti-inflammatory secreted molecules influences the final effect of this activation. Importantly, we identified an anti-inflammatory cytokine, TGF-beta, with neurogenic potential in the adult brain.

Melanoma, a Tumor Based on a Mutant Stem Cell?

Stem cells play a critical role in normal tissue maintenance, and mutations in these stem cells may give rise to cancer. We hypothesize that melanoma develops from a mutated stem cell and therefore residual stem cell characteristics should be able to be identified in melanoma cell lines. We studied three metastatic melanoma cell lines that exhibited multiple morphologic forms in culture and demonstrated the capacity to pigment. We used the ability to efflux Hoechst 33342 dye, a technique known to enrich for stem cells in many tissues, to segregate cell populations. The cells with the greatest ability to efflux the dye were (1) small in size, (2) had the capacity to give rise to larger cell forms, and (3) had the greatest ability to expand in culture. The small cells were found to have a decreased proliferative rate and were less melanized. Large dendritic cells that appeared to be nonproliferative were identified in cultures. Treatment with cytosine beta-D-arabinofuranoside hydrochloride (Ara-C) expanded the large cell population but the residual proliferative capacity, both in vitro and in vivo, remained concentrated in the smaller cell fraction. Antigenic staining patterns were variable and heterogeneous. Nestin (a neural stem cell marker) and gp100 (premelanosomal marker) favored the smaller cell population, while nerve growth factor receptor often labeled larger cells. Morphologic and antigenic heterogeneity remained intact after clonal purification. These findings are consistent with the behavior expected for a tumor based on stem cell biology; this finding has diagnostic and therapeutic implications for melanocytic neoplasias.

Transforming growth factor-beta and malignant melanoma: molecular mechanisms

Transforming growth factor family members (TGF-beta) are secretory polypeptides that have dual tumor-suppressor and oncogenic effects. They signal through kinase receptor complexes on the cell surface, which phosphorylate cytoplasmic mediators (SMADs). Upon phosphorylation, SMADs march to the nucleus and interact with coactivators or corepressors to mediate the transcriptional regulation of several genes resulting in diverse effects. In tumorigenesis, malignant cells escape from the tumor-suppressive effects of TGF-beta by mutational inactivation or dysregulated expression of the molecular components in TGF-beta signaling pathway. Although melanoma cells are resistant to the tumor-suppressive effects of TGF-beta, there are no detectable defects at the receptor/SMAD level. Therefore, in these lesions, it is possible that TGF-beta effects occur independently of TGF-beta receptor/SMAD pathway. This review seeks to examine the present knowledge about TGF-beta receptor/SMAD signaling pathway and its related genes (SMADs, SKI, Filamin, endoglin, Follistatin, and other molecules) in melanomas.

Bcl-2 Reduced and Fas Activated by the Inhibition of Stem Cell Factor/KIT Signaling in Murine Melanocyte Precursors

Stem cell factor (SCF) and its receptor, KIT, are essential to the migration and differentiation of melanocytes during embryogenesis. We previously demonstrated that apoptosis is induced by blocking survival function of the SCF/KIT interaction in a mouse neural crest cell (NCC) primary culture. Using the NCCmelb4 cell line, we investigated the occurrence of apoptosis in the cultured cells when KIT receptors were blocked by the monoclonal anti-KIT antibody (ACK2). Apoptosis following treatment with ACK2 was detected by DNA fragmentation assay, in situ apoptosis detection, and electron microscopy. We noted a decrease in extracellular signal-related kinase (ERK) and ribosomal S6 kinase (RSK) protein expression following ACK2 incubation. Western blot analysis and real-time quantitative RT-PCR revealed an apparent time-dependent reduction in Bcl-2 protein levels with respect to ACK2 within the NCCmelb4 cells. In terms of Bax expression, a difference was not found. Fas and caspase8 proteins increased time-dependently in proportion to ACK2 incubation. We noted apoptotic cell death upon addition of ACK2, with evidence of possible involvement of Bcl-2 and Fas in the induction of apoptosis. In contrast, no significant correlation between Fas ligand (Fas-L) expression and ACK2 was found. Fas activation appears to occur independent of Fas-L during ACK2-induced cell death. Therefore, we propose that Fas-L expression in NCCmelb4 cells does not play a major role in facilitating apoptosis. Furthermore, we hypothesize that these molecules combined with SCF/KIT play an important role in regulating the induction of vertebrate NCC apoptosis during embryogenesis.

Melanocyte Development: With a Message of Encouragement to Young Women Scientists

This is a semi-biographical review describing my research on melanocyte development and related personal experiences. Having been educated and trained as a dermatologist, I have been involved in many clinically-oriented studies, however, what has always interested me the most is pigment cell biology. Since I started working at St Marianna University in 1991, I have been undertaking research on melanocyte development and relevant growth factors using mice as models. My research in this field was inspired by my collaborations with various scientists, mostly from the field of biology. Many of these specialists I have met at meetings of the Societies of Pigment Cell Research (PCR). Stem cell factor (SCF, Kitl) and endothelin 3 (EDN3) have been identified as indispensable factors regulating the development of melanocytes. Mice mutant at loci encoding those factors (or their receptors) such as Sl/Sl (receptors W/W) and ls/ls (receptors s/s) have white coat colors and white patches, respectively. Our murine neural crest cell (NCC) primary cultures derived from Sl/Sl embryos showed that EDN3 cannot develop melanocyte precursors without SCF and that EDN3 can elicit proliferation and differentiation in the presence of SCF. These results suggest that without EDN3 and the endothelin type B receptor (EDNRB), melanocytes can not fully increase in number, which could well be the cause of the partial white coat color of ls/ls and s/s mice. Contamination with factors derived from the serum in medium or in feeder cells sometimes causes experimental errors, and therefore we established three immortal cell lines derived from NCC in different developmental stages and designated them as NCCmelb4, NCCmelb4M5 and NCCmelan5, all of which can survive without feeder cells. Using these cell lines and NCC primary cultures, we studied the effect of many factors related to melanocyte development. From the results, it has become evident that Vitamin D3 induces EDNRB expression by NCCmelb4 cells. In addition to the International Pigment Cell Conference (IPCC), I have also taken part in many annual meetings of the Japanese Society for Pigment Cell Research (JSPCR), Pan American Society for Pigment Cell Research (PASPCR) and European Society for Pigment Cell Research (ESPCR). Not only have I learned a great deal, I have enjoyed myself immensely at those meetings. Moreover, I have made many good friends there, some of whom I have collaborated with in my research. To conclude, I would like to give my message 'be ambitious' to young scientists, especially young women.

Developmental expression of BMP4/ALK3/SMAD5 signaling pathway in the mouse testis: a potential role of BMP4 in spermatogonia differentiation

It is well established that the c-kit gene plays an essential role in the proliferation of differentiating spermatogonia in prepuberal mice. However, the mechanisms that regulate the onset of spermatogenesis, i.e. differentiation of spermatogonial stem cells and c-kit expression, are poorly understood. Here we identify a novel signal transduction system in mouse prepuberal testis regulating this developmental event, involving bone morphogenetic protein 4 (BMP4) and its transduction machinery. BMP4 is produced by Sertoli cells very early in the postnatal life and is successively down regulated in peri-puberal Sertoli cells. Its receptor Alk3 and the R-Smad Smad5 are specifically expressed both in proliferating primordial germ cells and in postnatal spermatogonia. BMP4 stimulation of cultured spermatogonia induces Smad4/5 nuclear translocation and the formation of a DNA-binding complex with the transcriptional coactivator p300/CBP. In vitro exposure of undifferentiated spermatogonia to BMP4 exerts both mitogenic and differentiative effects, inducing [3H]thymidine incorporation and Kit expression. As a result of the latter event, Kit-negative spermatogonia acquire sensitivity to Stem Cell Factor.